scholarly journals Dual Regulation of Calcium Mobilization by Inositol 1,4,5-Trisphosphate in a Living Cell

2000 ◽  
Vol 115 (4) ◽  
pp. 481-490 ◽  
Author(s):  
Svetlana Tertyshnikova ◽  
Alan Fein
Keyword(s):  
Gene Expression ◽  
Living Cell ◽  
Enzyme Activation ◽  
Sustained Response ◽  
Common Mechanism ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Inositol 1,4,5 Trisphosphate ◽  
Dependent Inhibition ◽  
Stimulation Of

Changes in cytosolic free calcium ([Ca2+]i) often take the form of a sustained response or repetitive oscillations. The frequency and amplitude of [Ca2+]i oscillations are essential for the selective stimulation of gene expression and for enzyme activation. However, the mechanism that determines whether [Ca2+]i oscillates at a particular frequency or becomes a sustained response is poorly understood. We find that [Ca2+]i oscillations in rat megakaryocytes, as in other cells, results from a Ca2+-dependent inhibition of inositol 1,4,5-trisphosphate (IP3)–induced Ca2+ release. Moreover, we find that this inhibition becomes progressively less effective with higher IP3 concentrations. We suggest that disinhibition, by increasing IP3 concentration, of Ca2+-dependent inhibition is a common mechanism for the regulation of [Ca2+]i oscillations in cells containing IP3-sensitive Ca2+ stores.

scholarly journals LDL activates signaling pathways leading to an increase in cytosolic free calcium and stimulation of CD11b expression in monocytes

2003 ◽  
Vol 44 (7) ◽  
pp. 1332-1340 ◽  
Author(s):  
Ki Hoon Han ◽  
Yiming Chen ◽  
Mi Kyung Chang ◽  
Yoon Chan Han ◽  
Jae-Hyung Park ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Cd11b Expression ◽  
Stimulation Of

scholarly journals Control of inositol 1,4,5-trisphosphate-induced Ca2+ release by cytosolic Ca2+

1995 ◽  
Vol 306 (2) ◽  
pp. 445-451 ◽  
Author(s):  
M D Bootman ◽  
L Missiaen ◽  
J B Parys ◽  
H De Smedt ◽  
R Casteels
Keyword(s):  
Binding Site ◽  
Cell Types ◽  
Inhibitory Effects ◽  
Activation Curve ◽  
Hormonal Stimulation ◽  
A7r5 Cells ◽  
Inositol 1,4,5 Trisphosphate ◽  
Insp3 Receptors ◽  
Dependent Inhibition ◽  
Stimulation Of

The synergistic action of cytosolic Ca2+ and inositol 1,4,5-trisphosphate (InsP3) in releasing intracellular Ca2+ stores has been suggested to be responsible for the complex intracellular Ca2 signals observed during hormonal stimulation of many cell types. However, the ability of cytosolic Ca2+ to potentiate Ca2+ release has recently been questioned because of the observed inhibitory effects of Ca2+ chelators used in previous studies. In the present study, EGTA and BAPTA [1,2-bis-(2-amino-phenoxy)ethane- NNN'N′-tetra-acetic acid] poorly inhibited InsP3-induced Ca2+ release from permeabilized A7r5 smooth-muscle cells. Additionally, stimulatory effects of cytosolic and luminal Ca2+ were observed either in the complete absence of Ca2+ chelator or at constant Ca(2+)-free chelator concentration. These data suggest that potentiation of InsP3-induced Ca2+ release by Ca2+ in A7r5 cells reflects an interaction between Ca2+ and InsP3 receptors, rather than a decrease in chelator-dependent inhibition. The EC50 for activation of InsP3-induced Ca2+ release by cytosolic Ca2+ was unaffected by ATP, or by changing InsP3 concentration, although InsP3-induced Ca2+ release became less sensitive to the inhibitory effects of cytosolic Ca2+ as the InsP3 concentration was elevated. Increasing H+ or Mg2+ concentration shifted the Ca(2+)-activation curve towards higher Ca2+ concentrations. These data suggest that, in addition to the InsP3-binding site, the affinity of the Ca(2+)-binding site(s) on InsP3 receptors can be modulated by intracellular cations.

TRI-IODOTHYRONINE INCREASES INTRA-CELLULAR CALCIUM LEVELS IN SINGLE RAT MYOCYTES

1991 ◽  
Vol 7 (1) ◽  
pp. 77-79 ◽  
Author(s):  
R.B. Lomax ◽  
P.H. Cobbold ◽  
A.P. Allshire ◽  
K.S.R. Cuthbertson ◽  
W.R. Robertson
Keyword(s):  
Ventricular Myocytes ◽  
Single Cells ◽  
Mean Amplitude ◽  
Free Calcium ◽  
Acute Administration ◽  
Cytosolic Free Calcium ◽  
Rat Hearts ◽  
Rat Myocytes ◽  
Stimulation Of

ABSTRACT We have studied the effects of acute administration of tri-iodothyronine (T3) on cytosolic free calcium levels [Ca2+]i in single rat myocytes microinjected with aequorin. Ventricular myocytes were isolated by perfusing rat hearts with collagenase, and healthy, rod-shaped cells were injected to <1% of their volume with aequorin. The photons emitted from single cells were measured and a conversion to [Ca2+]i made on the basis of an in vitro calibration after the remaining aequorin had been discharged by cell lysis. Only cells that depolarized reversibly (showing elevated [Ca2+]i levels) when superfused with 80mM KC1, and which gave a substantial signal on lysis with distilled water were used. The [Ca2+]i rose from a resting value of 150±56nM (mean ± SD, n=14) by 127±47nM on depolarization with 80mM KC1. Application of T3 (1-100nM) led to an increase (P<0.05) in [Ca2+]i (mean amplitude of 152±35nM) before returning to baseline. The median duration of these events was 10 min (range = 1.4-34.4 min). The time to response was shorter when lOOnM T3 was applied (median and range; 6.8, 0-14 min) than when 1nM T3 was used (16, 7.0-56.1 min) (P<0.05). To conclude, physiological concentrations of thyroid hormones caused rapid but transient stimulation of [Ca2+]i in single rat myocytes.

Relation between cytosolic free calcium and respiratory rates in cardiac myocytes

1988 ◽  
Vol 255 (2) ◽  
pp. H347-H357 ◽  
Author(s):  
R. Moreno-Sanchez ◽  
R. G. Hansford
Keyword(s):  
Cardiac Myocytes ◽  
Ruthenium Red ◽  
Free Calcium ◽  
Small Decrease ◽  
O2 Uptake ◽  
Cytosolic Free Calcium ◽  
Total Inhibition ◽  
Uptake Rates ◽  
Rat Cardiac Myocytes ◽  
Stimulation Of

Rates of O2 uptake of isolated rat cardiac myocytes were determined as a function of cytosolic free Ca2+ concentration ([Ca2+]c) that was estimated from intracellular quin2 fluorescence. [Ca2+]c was increased by depolarization with K+ or veratridine. In each case, there was a correlation between increase in [Ca2+]c and stimulation of O2 uptake. Apparent exception seen on raising K+ were resolved on the of an effect of osmolality on O2 uptake rates. Increase in O2 uptake and [Ca2+]c by veratridine was sensitive to variation of extracellular Na+, Ca2+, and pH in a way that suggests a major involvement of the Na+-Ca2+ exchange: partial inhibition by 2.7 microM verapamil and total inhibition by 30 microM 3',4'-dichlorobenzamil were consistent with this conclusion. Attempts were made to assess the quantitative significance of direct activation of respiration by Ca2+ at the level of mitochondrial dehydrogenases vs. an indirect mechanism involving increased ADP generation. Ruthenium red, which blocks the former process but not the latter, gave a small decrease in O2 uptake rates. However, activation of oxidative phosphorylation by ADP was predominant under these conditions of profound and sustained depolarization, based on a lowered mitochondrial NADH content in response to veratridine.

Sign in / Sign up

Export Citation Format

Share Document